JPS5975810A - Improved pneumatic radial tire - Google Patents

Abstract

PURPOSE:To improve the stability of steering and the wet performance and sharply reduce the rolling resistance by properly varying the profile of the radial surface of a carcass and providing proper physical properties to rubber filler. CONSTITUTION:When a tire is mounted on a rim 7 and a regular inside pressure is applied, the point at which a line drawn horizontally-from the point A intersects a carcass 3 is defined as B, and the point at which a perpendicular drawn from the point B intersects the carcass 3 is defined as C. The midpoint of a segment BC is defined as D, and the intersection of a horizontal line passing through a point D and a perpendicular passing through the widest point F of the carcass is defined as E. The intersection of a line passing through the midpoint H of a segment GC and the carcass 3 is defined as I, the radius of a circle passing through the points F, I, and C is defined as R, and the radius of a circle passing through the point B, E, and C is defined as R'. The carcass has the profile of a radial surface with the R/R' in the range of 0.65-0.85 and with (f) of 5-10mm., and the rubber filler 2 has the characteristics of 80 to 97 deg. by the Shore A hardness, modulus of 80-65kg/cm<2> at a elongation of 25%, and 0.4-0.6 by the loss factor.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to an improved pneumatic radial tire,
In particular, we are focusing on appropriately changing the carcass radiation surface profile of this tire and giving the rubber filler appropriate physical properties, such as rolling resistance, handling stability, vibration riding comfort, and wetness. This is an attempt to simultaneously improve the performance that is important for tires in a well-balanced manner.

It has been said that in order to reduce the rolling resistance of tires, it is necessary to reduce the energy consumed by stress and strain cycles associated with tire rolling. In this respect, conventional tires with a so-called radial carcass structure, which have been generally recognized as being practical, are used under normal usage conditions, that is, when they are inflated with an internal pressure of no more than 2'q/cm. According to the results of an analysis of the proportion of energy consumed by each component of the tire in the entire tire, approximately 84% of the energy is consumed in the tread, 27% in the padless part, 25% in the sidewall part, and 141% in the bead part. It was found that it can be treated as a

The tread part has the largest contribution to rolling resistance, and therefore, in order to reduce the internal friction of this tread rubber and reduce rolling resistance, a rubber compound that increases the rebound modulus (Re5ilisnoe) of this rubber is used. It is common to deal with this by However, in this case, the disadvantage is that the wet performance, which is one of the important characteristics of this type of tire, deteriorates undesirably depending on the degree to which the rolling resistance is improved.

Therefore, the above measures cannot be expected to dramatically improve rolling resistance unless other measures are taken to prevent deterioration of wet performance.
And since there is no particularly effective means for maintaining wet performance, in the end it cannot be very effective.

As a second-best measure, attempts have been made to apply a rubber compound that reduces internal friction to the sidewalls in much the same way as described above regarding the characteristics of tread rubber, but in reality, it has not reached the 8th factor of rolling resistance, or even that. However, this method has the disadvantage that the damping characteristics of the vibration generated in the tire are deteriorated, which is accompanied by a disadvantage in the important ride comfort performance of the tire.

In addition, methods have been adopted to reduce the weight and rolling resistance of tires by changing the structure from two layers to one, or by narrowing the width of the belt. - It is unavoidable that there is a limit to its effectiveness, as it leads to a decrease in steering stability due to a decrease in the rigidity of the main part of the tire, which is important for tire reinforcement.

As shown above, when trying to improve rolling resistance,
The trade-off between this and other tires is clear: important performance for other tires deteriorates. This is from the literature (D, J Sch
uring', IIThe Rolling' L
oss or Pnsu -ffiatiOTires
n Rubber(3hsmistry and Te
Chnology.

Vol. 58, 8.1980), etc.
Therefore, how to resolve this contradictory question order is an important issue that has not yet been resolved.

This invention departs from the conventional thinking as described above and changes the radial surface profile of the carcass at an appropriate pressure, thereby significantly reducing rolling resistance and improving handling stability, wet performance, etc. It stems from new research into what can be advantageously realized.

Regarding conventional attempts to improve rolling resistance by changing the carcass radial surface profile, for example, as seen in Japanese Patent Application Laid-Open No. 54-40406, the tire's aspect ratio was increased from 55 to 65. Oval-shaped pneumatic radial tires for passenger cars are known, in which it is essential to reduce the tire size and use a so-called natural equilibrium shape as the radiation surface profile of the carcass.

However, the carcass radiation surface profile of this invention is
It is a shape in which the natural equilibrium shape is deliberately damaged, and it can be applied to tires of any aspect ratio, especially when a load is applied to a radial carcass tire and the deformation of the sidewall that occurs when the tire rolls. This was arrived at as a result of fundamental research into the matter.

It is a well-known fact that sidewall deformation can generally be divided into bending deformation and shearing deformation, but in this invention, as a result of further detailed consideration of this point, the lower sidewall region (near the bead) ), the contribution of bending deformation is large;
This is derived from the discovery of a difference in the deformation mode in which the contribution of shear deformation is large.

The shearing deformation in the upper region of the sidewall exhibits more complicated behavior than the bending deformation, but the inventors obtained the following important findings as a result of examining the amount of lead.

First, when a load is applied to the tire and it is rolling, the shear deformation in the area above the sidewall is small immediately under the load, but increases significantly near the point where it enters and leaves the contact patch, and has a large impact on energy consumption as a whole. Second, shear deformation has an inverse correlation with bending deformation, and as bending deformation increases, shear deformation decreases.

Based on the above knowledge, the upper part of the sidewall is a relatively thin part, and even if the bending deformation that occurs concentrated directly under the load is slightly increased, the shear that makes a very large contribution to energy consumption By reducing deformation,
It has become clear that overall energy consumption can be reduced.

In order to increase the bending deformation in the upper area of the sidewall,
When the tire is assembled to a regular rim and filled with the regular internal pressure, it is necessary to increase the curvature of the contour curve of the shoulder part of the carcass corresponding to the upper region of the night wall, and the inventors have determined the radius of curvature R° of this curve. As a result of various studies, we found that the above objective can be advantageously achieved when the ratio R/R' to the radius R' of the reference arc shown in FIG. 1 and explained later is in the range of 0.65 to 0.85. I found something that fits.

What should be noted here is that the arc BEO shown in Figure 1 is just a reference arc, and although it is originally different from the carcass radiation surface profile based on the so-called natural equilibrium shape, the area above the sidewall is Since the thickness of the carcass is relatively thin and its rigidity is low, the carcass radiation surface profile based on the natural equilibrium shape is very similar to a portion EC of this circular arc.

That is, 0.65 to 0.8 with respect to the above ratio R/R'
It must be noted that a value of 5 can only occur as a result of deliberately deviating from the natural equilibrium shape.

When R/R' is larger than 0.85, the natural equilibrium shape is intentionally removed to reduce shear deformation in the upper side portion, and the rolling resistance is sufficiently improved, as shown in the examples later. Also, R/R' is 0.6
If it is less than 5, bending deformation will concentrate on the comparatively thick buttress portion of 17 mm, and the effect of improving rolling resistance obtained by reducing shear deformation will be negated.

Next, considering energy consumption due to bending deformation in the lower region of the sidewall, it can generally be expressed as in the following equation.

Energy consumption = A-E-tanδ・(Δa) −8−
(1) However, A: Appropriate constant E: Elastic modulus of the lower region of the sidewall Δ0: Change in curvature of the lower region of the sidewall due to bending deformation S: Length of the lower region of the sidewall measured from the maximum width point of the carcass Therefore, It is clear that if E, tanδ and S are equivalent, energy consumption is proportional to (Δ○).

As a result of investigating changes in the curvature of the lower sidewall area when a load is applied to an actual tire, the inventors obtained the following important findings.

In other words, as shown in Figure 2, when a normal load is applied to the tire, the lower sidewall area becomes deformed into an inverse R, which means that before the load deformation, it had an outwardly convex radius of curvature R□. However, after the deformation, a deformation occurs in which the radius of curvature R2 of the concave shape is reversed outward. Here (1)
The curvature change (ΔC) in the lower region of the sidewall in the equation can be expressed by the following equation.

Here, if the lower area of the sidewall already has a reverse radius fc when the 4-year ear is attached to the regular rim and filled with the regular internal pressure, the curve change (ΔC') will be 2 orders of magnitude, Obviously, the force is smaller than (ΔC) according to the above equation (9), and the energy consumption according to the equation (1) can be reduced in proportion to it.

From this perspective, in the lower sidewall area.

It is effective to give an inverted R shape under normal internal pressure filling, but
Especially considering that bending deformation occurs centering on the carcass, which bears the filling internal pressure, it is most desirable to invert the curvature of the carcass itself.

As a result of various studies on the extent to which the curvature of the carcass is reversed, the inventors were able to consider the value of f, which is the maximum distance between the carcass line FB and the circular arc BE shown in FIG. It was found that f is 5 mm -, -l Q mm as a suitable range of 4.

As mentioned above, the circular arc BgO is simply a reference circular arc, and is different from the carcass radiation surface profile based on the so-called natural equilibrium shape.

In particular, the area below the sidewall has relatively high rigidity because the carcass is rolled up radially outward around the bead core, and the bead part is hardened by filling the rolled up part with rubber filler. The carcass radiation surface profile based on the natural equilibrium shape generally exists inside the circular arc BE.

However, f shown in this invention is 5 mm - 10 m
The value m can only be obtained by intentionally removing the natural equilibrium shape and inverting the curvature of the carcass in the lower sidewall region, and is a value that can be completely distinguished from the conventional natural equilibrium shape. If f is less than 5 mm, the principle shown in equations (1) to (8) above will not be able to sufficiently reduce energy consumption, and f will exceed l Q mm. When filling the internal pressure, the tension in the carcass in the area below the sidewall becomes too high, which not only has a negative effect on durability, but also causes the outer surface of the tire to be located relatively inside the tire as the carcass moves inside the tire. This results in disadvantages such as poor compatibility with the rim.

As mentioned above, the tire according to the present invention has a carcass radiating surface of 7" o file which intentionally deviates from the so-called natural equilibrium shape, and in order to manufacture such a tire, a patent application previously filed is required. 2. There is a jacket with a device as shown in No. 57-40281.

The tire of the present invention is a tire in which the natural equilibrium radial surface profile has been deliberately removed, and can be easily identified from the outside by observing the change in the carcass radial surface profile during filling of the tire's internal pressure.

In other words, when the tire is mounted on the rim and the internal pressure is filled to the 5th part of the normal internal pressure, the deformation when filling is the so-called natural equilibrium carcass radial surface profile is 185/705R14 in Fig. 8. As shown in the example of the size, protruding deformation occurs substantially uniformly over the entire sidewall portion, whereas in the mixing of the carcass radial surface profile according to the present invention, as shown in FIG. The amount of protrusion deformation is much larger, and although some protrusion deformation occurs in the area above the maximum middle position, there is no substantial deformation. In FIGS. 8 and 4, solid lines and broken lines indicate the outer surface shapes of the tire at the front and rear holes of the protruding deformation, respectively, which were molded with plaster.

It goes without saying that the difference in deformation caused by this internal pressure filling affects the tension distribution in the carcass. In the case of the tire according to the present invention, the carcass tension is high in the vicinity of the heed portion where the amount of protrusion deformation is large, and the apparent rigidity is high, but on the other hand,
Since the amount of protruding deformation from the upper part of the sidewall to the buttress part is small, the tension in the carcass is relatively low and the apparent rigidity is also low. and,
This feature, as described below, not only improves rolling resistance, but also affects handling stability, wet performance, and vibration riding comfort.

First, let's consider the case where a slip angle is added to the tire. At this time, a lateral force acts on the tire, resulting in a lateral deformation, but in the case of the tire of this invention, the carcass tension near the bead is high and the apparent rigidity is large. The stiffness against lateral deformations is also increased, resulting in high cornering power and good stability, especially at high slip angles.

This improvement is most clearly seen when the road surface is dry, i.e., on a dry road surface, but it is also exhibited when the road surface is wet, i.e., on a wet road surface. This can be clearly understood as the difference in running time required for slalom running on the same trajectory.

Next, let's consider the vibration ride quality when a tire rides over a protrusion on the road surface. A normal radial tire has multiple belts embedded in the crown that are made up of cords with a high elastic modulus that intersect the tire's equator at a very shallow angle, so the bending rigidity in the thickness direction of the tread is extremely high. During road transfers, when driving over bumps on the road, the tread deforms sufficiently and the impact that occurs here is not fully absorbed by the sidewall and is transferred from the tire bead to the rim wheel and axle. Therefore, the key to improving vibration riding comfort is how to absorb and attenuate the impact between the tire sidewall and the ped.

Preferably, the radial surface profile according to the present invention has the advantage that the ply tension from the upper sidewall region to the buttress portion is low and the apparent stiffness is small, so that impact absorption is improved.

On the other hand, regarding the damping property of shock vibration, the function of damped vibration is expressed by the following formula, F(t)=B/Sin[2π(t-to)/T)
・”(4) However, F(t,): Impact force B: Imaging amplitude r: Attenuation coefficient T: Time until the weekly imaging amplitude B attenuates to B/l, that is, the following formula % formula As a result of comparing the case of the carcass radiation surface profile of the present invention with %(5) as the decay time and the case of the natural equilibrium carcass radiation surface profile, the present invention will be explained later using specific numerical values. In the case of the carcass radial surface profile of Sidewall 2, the ply tension is low from the upper area to the buttress area, and the apparent rigidity is low, so the damping time is slightly longer.In other words, the damping time is slightly longer. It was found that vibrations tend to be difficult to damp.

Therefore, if the above-mentioned attenuation characteristics can be improved by using the carcass radiation surface profile of the present invention, as described at the beginning. This is thought to solve the trade-off between improving rolling resistance and deteriorating other tire performances.

For this reason, the method discovered by the inventors is to use a rubber filler that is hard and has large hysteresis loss characteristics, that is, Shore A hardness Ht5) of 80° to 97°.
Modulus at 25° extension is 89kf/crn” ~
(5ft kg/cm 1 loss tangent (tan δ) is 0.
The goal is to arrange rubber that has characteristics of 4 to 0.6. The reasons why such a physical property range is preferable and the advantages thereof are summarized as follows. (1) The tire of the present invention has sidewalls like a so-called run-flat tire (puncture-free tire).
This is based on a general radial tire that does not use a special reinforcing rubber layer on the tire.

Particularly, in order for the carcass to maintain a reverse direction ratio in the area below the sidewall, and for the above f to be in the range of 5 mm to 1 mm, it is necessary to provide large bending rigidity in advance near the pead. However, reinforcing the vicinity of the bead using more reinforcing members than necessary impedes the improvement of rolling resistance, which is one of the objectives of the present invention, and this poses the difficulty of selecting appropriate members. The inventors have discovered that the appropriate selection of members is that the rubber filler has a Shore A hardness (
H6) is made of a hard rubber stock with an angle of 80° to 97° and a modulus at 2b elongation of ao kg/6n-65#/cm. Here the hardness is 800.
It is difficult to maintain a carcass radiation surface profile intentionally removed from the natural equilibrium carcass radiation surface profile with rubber whose modulus is less than Bθ h/cfn.
Hardness is 970. 25th modulus is 65 kg/cm
Although larger rubbers are better at maintaining the carcass radial profile, they come with associated durability disadvantages.

(2) In this way, if the carcass radiation surface profile intentionally removed from the natural equilibrium carcass radiation surface profile can be maintained, the curvature change in the lower region of the sidewall can be reduced as shown in equations (1) 2 to (8) above, Since the contribution of the bead portion to the energy consumption of the entire tire becomes small, even if the hysteresis loss characteristic of the rubber filler is increased, there is virtually no deterioration in rolling resistance. As mentioned above, handling stability, wetness, and vibration absorption are improved.

(8) Although the impact absorption properties of the upper part of the sidewall are improved due to the characteristics of the carcass radiation surface profile, the impact vibrations that are not completely absorbed and are transmitted greatly affect the hysteresis loss characteristics of the rubber filler. By doing so, vibration is damped and ride comfort performance is also improved. If the loss tangent of the rubber filler is less than 0.4, such an effect will not be fully exhibited, and if the loss tangent is greater than 0.6, the carcass radiation surface profile of this invention will not be maintained. Even if it is, the rolling resistance will deteriorate.

As described above in detail, the present invention, as shown in FIG. At least one layer of carcass 8 is rolled back with a pincher and stretched outward in the radial direction of the tire; At least two layers of the belt 4 which are rubber coatings of high elastic cords are provided as body reinforcements that work together with each other, the rubber of the sidewall 5 is placed on both sides of the carcass 8, and the rubber of the tread portion 6 is placed on the outer periphery of the belt 4. When the tire is mounted on the regular rim 7 and filled with the regular internal pressure, the point at which the outer surface of the tire begins to separate from the rim's 7 lunge is M, A.
B is the point where carcass 8 intersects with a straight line drawn parallel to the tire rotational axis from point B to the inside of the tire, and D is the point where carcass 8 intersects with a perpendicular line drawn in the direction of the center diameter from point B, the midpoint of O99 layer B0. A straight line drawn through the point parallel to the tire rotation axis,
E is the intersection point with a straight line that passes through the maximum midpoint F of the carcass and is perpendicular to the axis of rotation of the tire.

G is the intersection of the line segment BO and a straight line drawn from point F, which is the maximum midpoint of the carcass, to the inside of the tire parallel to the axis of rotation of the tire.
The midpoint of the line segment %GO is H, the intersection of the straight line drawn parallel to the tire rotation axis through the H point and the carcass 8, points F, I
, C! , the radius of the circle passing through point B, E, and O is R', one part FB of carcass 8, and arc B.
A radiation surface where R/R' is in the range of 0.65 to 0.85 and f is in the range of 5 mm % l Omm, respectively determined as the maximum distance f as seen in the normal direction of the circular arc between E and E. The rubber filler 2 has a shore A hardness and a modulus of 8 Q kg/cm to 65 kg/lyn when elongated at 25 degrees from 80° to 970°.

A pneumatic radial tire characterized by a loss tangent of 0.4 to 0.6.

Although the left half of the tire shown in FIG. 5 has been described above, the tire is symmetrical with respect to the equatorial plane 0-0, and illustration of the right half has been omitted.

Here, the carcass 8 can be made of organic fiber cord such as polyester, nylon, rayon, or aromatic polyamide fiber (Kevler).
For this purpose, metal cords such as steel, organic fiber cords such as rayon, polyester, and aromatic polyamide fibers, and non-stretchable cords such as glass fiber cords are used at a shallow angle of 10 to 25 degrees to the tire equator. A plurality of angularly oriented layers are applied one on top of the other, with the layers intersecting each other.

Regarding the lamination of the belt 4, a heat-shrinkable material such as a nylon cord was arranged approximately parallel to the tire equator on both edges of each layer of the belt 4, left separated, or on the outer periphery of the laminated layers. Use of an auxiliary ply that covers at least the edge of the belt in one or more layers, folding both edges of at least one of each layer of the belt to the inside or outside of another belt, or separating the edge of the belt. It may also be a known arrangement of rice plants that are wrapped and overlapped.

As mentioned above, this invention uses a rubber stock that is hard and has high hysteresis loss characteristics as a rubber filler, and intentionally deviates from the natural equilibrium carcass radiation surface profile.
The carcass radiation surface profile is maintained during normal internal pressure filling, and the attenuation characteristics against shock imaging are improved.

Such effects are obtained not only when the rubber filler is composed of a single rubber stock, but also when the rubber filler is composed of two or more types of rubber stocks.
Even when the rubber filler is V, by giving the rubber stock with the largest volume hardness and high hysteresis characteristics, the rubber filler can perform almost the same as when it is made of a single rubber stock. I can do things.

In addition, the above rubber filler has a tapered shape, and the height measured from the bead base at the tip position is 40 inches to 75% of the height measured from the bead base at the maximum midpoint of the carcass.
It is desirable that it be within the range of . This means that the height to the tip of the rubber filler is 40 times the height to the maximum width point.
The maintenance of the carcass shape of this invention is easy, and also 7
This is because if the number of scratches exceeds 5, the rubber filler will be placed in a position where bending deformation is extremely large, and the high hysteresis loss characteristic of the rubber will lead to deterioration of rolling resistance.

Next, the effects of the present invention according to the configuration described above will be explained using examples.

The contents of the tire of the example and the tire of the comparative example are as shown in Table 1. As the carcass 8, a high modulus polyester cord of 15006/2 was used as the tire equator, and 9
One braai arranged at 0° is used, and the belt 4 is made of two steel cords (twisted structure 1×5×Q, 25 mm) that are crossed with each other at a cord angle of 17° with respect to the tire equator.

Here, the loss tangent of Comfila is determined by a mechanical spectrometer (manufactured by Rheometrics) at 50°C, 15Hz,
This is the result of measurement under the condition of distortion imaging width 11.

The carcass radiation surface profiles of Comparative Example 1.2.8 and Examples 1 and 2.8 are as shown in FIG. 6, and the rubber filler of Example 8 is as shown in FIG. It consists of

First, Table 2 shows the results of comparing the rolling resistance values of these tires. Here, the index of Comparative Example 1 is set to 100, and the larger the index, the better the rolling resistance [7].
ing. In addition, the rolling resistance test was conducted using a diameter of 1707 m.
After pressing the tire against the drum and driving it to rotate until it reaches vermilion, let it coast and calculate from the degree of deceleration during the rotation of the joint W.

From this table, it can be seen that large I
It is clear that an improvement in rolling resistance has been brought about. What is most noteworthy is that the degree of improvement in rolling resistance did not substantially decrease even in Example 1.2.8 of the present invention, in which a rubber stock with high hysteresis loss characteristics was used as a comb filler. The reason for this is as explained in detail above.

Next, Table 8 shows a comparison of the cornering power and the maximum value of the cornering force when a slip angle is added to these tires. Here, it is shown that the larger the cornering power is, the better the steering performance is, and the larger the maximum value of the cornering force is, the better the stability performance is.

The results show that the tires having the carcass radial surface profile of the present invention (Comparative Example 8 and Example 1°2.8) are excellent in maneuverability and stability.

This tendency is observed even when the road surface is wet, and when tires are actually installed on a car, it is the same on a wet concrete road surface (skid ASN = 85, which indicates road roughness) and an asphalt road surface (sa = +sO). When comparing the time required to run a slalom over the same distance over the same trajectory, it was clear that the tire having the carcass radial surface profile of the present invention had an improvement of 2 to 8 inches in terms of index.

Next, the magnitude of the amplitude of the force generated on the rotating shaft of the rotating tire was measured using a test drum with protrusions on the similar tire, and the absorbency of impact vibration was determined as described in (4) above.

Table 4 shows the results of calculating the damping time of impact vibration using equation (5), evaluating the damping performance against vibration, and comparing the quality of the vibration riding comfort performance. Here again, the larger each index means the better the vibration absorption performance and damping performance.

In this table, Comparative Example 8 has the carcass radiation surface profile of this invention, but because the loss tangent of the rubber filler is different from that of this invention, the attenuation characteristics for shooting when going over a protrusion are slightly deteriorated. It is clear that there are. On the other hand, Example 1.2 is a tire having both the carcass radiation surface profile of the present invention and the loss tangent value of the rubber filler,
The damping characteristics for shooting when going over a bump have been significantly improved,
It is also clear that this has a positive effect on absorbency for photographing. Furthermore, as shown in Example 8, when the rubber filler is composed of two types of rubber stocks and the loss tangent of the present invention is given to the rubber stock with a larger volume, the loss tangent of the present invention is substantially the same as in Examples 1 and 2. It must be noted that the same effect is observed.

Furthermore, when similar tires were subjected to high internal pressure and stomach load and the distance until failure on the drum was compared, the tire of the example of this invention had exactly the same durability performance as the tire of Comparative Example 1. .

As shown above, according to the present invention, by appropriately determining the radiation surface profile of the carcass and arranging rubber stock having high hysteresis characteristics as a rubber filler, rolling resistance can be significantly reduced. In addition, steering stability performance, wet performance, absorption and damping performance for photographing can be improved all at once, and the trade-off between reducing rolling resistance and deteriorating other important performances can be resolved.

[Brief explanation of the drawing]

Figure 1 shows the radial surface profile (
Figure 2 is an illustration of the deformation behavior when a normal load is applied to the tire. Figure 8 is the internal pressure filling of a tire with a natural equilibrium carcass radial surface profile. FIG. 4 is an explanatory diagram of deformation behavior due to internal pressure filling of a tire having a carcass radial surface profile according to the present invention. FIG. 5 is a sectional view of a tire according to the present invention. FIG. 6 is an embodiment of the present invention. FIG. 7 is an explanatory diagram showing the structure of the rubber filler of Example 8 of the present invention. 1... Bead core? ...Rubber filler, 8...
・Carcass, 4... Belt, 5... Side wall, 6... Crown part, 7... Regular rim, R... Radius of curvature of the shoulder limbus curve of the carcass line, R'...・Radius of reference arc. Patent applicant Brideston Tire Co., Ltd. No. 11 Figure 5

Claims (1)

[Scope of Claims] 1. It has a pair of annular sidewall parts each having a peed part and a crown part spanning the radially outer sides of these sidewall parts, and each of these parts is connected to at least one blind layer of an organic fiber cord layer. It consists of a carcass with both ends of the bra wound outwards around the peed core buried in each bead, and a carcass wrapped around this carcass at a relatively small angle with respect to the center circumference of the tire. The tire is reinforced with at least two layers of rubber-coated iK belts made of high-modulus cords arranged in a cross-arranged manner, and a rubber filler is filled between the carcass and the ply rewind to harden the bead part, and the regular rim of the tire is reinforced. In combination with the carcass line and a straight line parallel to the axis of rotation of the tire passing through the separation point from the outer surface of the bead of the flange of the rim under the mounting position filled with the normal internal pressure, , passing through the end point O of a line segment that is perpendicular to the above straight line and reaching the carcass line, with a distance equal to the maximum separation distance of the carcass line from the line segment, and the radius R' of a reference arc hypothesizing the line segment as a chord. R/R of the radius of curvature R of the shoulder contour curve passing through the end point O of the carcass line to
' is in the range of 0.65 to 0.85, and the maximum distance f from the reference arc of the residual area of the carcass line that smoothly continues with the curve and has a single inflection point while reaching the intersection B has a carcass radial surface profile in the range of 5 to lOmrrL, and the rubber filler has a Shore A hardness of 80°
~97°, modulus at 25 extension is 80 k4/cm
An improved pneumatic radial tire characterized in that it has at least in part a hard rubber stock having physical properties in the range of 0.4 to 0.6 with ~65 snout/- and loss tangent. 2. The tire of claim 1, wherein the λ rubber filler is a composite of a hard rubber stock and one or more rubber stocks having a smaller volume and having other properties. & The rubber filler has a tapered shape outward in the tire radial direction, and the height measured from the bead base at the tip position is within the range of 4091i to 75in the height measured from the bead base at the maximum midpoint of the carcass. A tire according to claim 1m or 2.